Circulation in a Short Cylindrical Couette System

Kageyama, Akira ; Ji, Hantao ; Goodman, Jeremy

Princeton University. Plasma Physics Laboratory.

关键词: Mhd Instability;    Liquid Metals;    70 Plasma Physics And Fusion Technology;    Accretion Disks;    Couette Flow;   

DOI  :  10.2172/814703
RP-ID  :  PPPL-3836
RP-ID  :  AC02-76CH03073
RP-ID  :  814703

美国|英语

来源: UNT Digital Library

【 摘 要 】

In preparation for an experimental study of magnetorotational instability (MRI) in liquid metal, we explore Couette flows having height comparable to the gap between cylinders, centrifugally stable rotation, and high Reynolds number. Experiments in water are compared with numerical simulations. The flow is very different from that of an ideal, infinitely long Couette system. Simulations show that endcaps co-rotating with the outer cylinder drive a strong poloidal circulation that redistributes angular momentum. Predicted toroidal flow profiles agree well with experimental measurements. Spin-down times scale with Reynolds number as expected for laminar Ekman circulation; extrapolation from two-dimensional simulations at Re less than or equal to 3200 agrees remarkably well with experiment at Re approximately equal to 106. This suggests that turbulence does not dominate the effective viscosity. Further detailed numerical studies reveal a strong radially inward flow near both endcaps. After turning vertically along the inner cylinder, these flows converge at the midplane and depart the boundary in a radial jet. To minimize this circulation in the MRI experiment, endcaps consisting of multiple, differentially rotating rings are proposed. Simulations predict that an adequate approximation to the ideal Couette profile can be obtained with a few rings.